We report on alkaline hydrolysis of tetraethoxysilane (Stöber synthesis) inside a macroporous polymer matrix resulting in a homogeneous coverage of silica onto the polymer surface. The encapsulation of the polymer struts by a continuous silica crust allows further functionalization with hydrophilic and hydrophobic silylating agents. The porous silica polymeric hybrid material combines the morphological control and mechanical flexibility of the polymeric matrix with the convenient surface modifications developed for glass and amorphous silica. This concept is applied to macroporous membranes where alteration in surface functionality allows tuning of hydrophobicity (contact angle and liquid entry pressure), streaming potential, and adsorption capacity of double-stranded DNA.